RFR: 8074895: os::getenv is inadequate

[Jeremy Manson]

I hate to see legacy cruft deliberately introduced into the codebase.  I
guess it is too painful to turn it off in a makefile?  Stuff ignored by
compilers in rarely touched code like this tends to turn crufty and become
confusing, e.g., something I saw a month or two ago:

http://hg.openjdk.java.net/jdk9/dev/hotspot/file/f68d656d1f5e/src/share/vm/oops/instanceKlass.cpp#l784

Referring you to a page in what you have to think about for a second before
you realize is JVMS v1, which has been obsolete since 2000, and is
unavailable from the publisher.

Doing it this way seems fine to me, but I don't know anything about
suppressing warnings on Windows, so that's not a firm endorsement.  Not
that my non-reviewer endorsement would do you any good.

Jeremy

On Wed, Mar 25, 2015 at 11:41 PM, David Holmes <david.holmes at oracle.com>
wrote:

> Okay I managed to fix this with:
>
> --- old/src/share/vm/utilities/growableArray.hpp        2015-03-26
> 02:34:35.715892476 -0400
> +++ new/src/share/vm/utilities/growableArray.hpp        2015-03-26
> 02:34:34.663833288 -0400
> @@ -168,6 +168,8 @@
>    GrowableArray(int initial_size, bool C_heap = false, MEMFLAGS F =
> mtInternal)
>      : GenericGrowableArray(initial_size, 0, C_heap, F) {
>      _data = (E*)raw_allocate(sizeof(E));
> +// Needed for Visual Studio 2012 and older
> +#pragma warning(suppress: 4345)
>      for (int i = 0; i < _max; i++) ::new ((void*)&_data[i]) E();
>    }
>
> @@ -385,6 +387,8 @@
>      E* newData = (E*)raw_allocate(sizeof(E));
>      int i = 0;
>      for (     ; i < _len; i++) ::new ((void*)&newData[i]) E(_data[i]);
> +// Needed for Visual Studio 2012 and older
> +#pragma warning(suppress: 4345)
>      for (     ; i < _max; i++) ::new ((void*)&newData[i]) E();
>      for (i = 0; i < old_max; i++) _data[i].~E();
>      if (on_C_heap() && _data != NULL) {
>
> So unless someone finds this totally objectionable it is what I propose to
> go with. Full webrev at:
>
> http://cr.openjdk.java.net/~dholmes/8074895/webrev/
>
> Thanks,
> David
>
>
> On 25/03/2015 2:24 PM, David Holmes wrote:
>
>> On 24/03/2015 2:56 AM, Jeremy Manson wrote:
>>
>>> Thanks, Kim.  This is a pretty silly warning to have break the build.
>>> Does anyone have a problem with PODs being default initialized?  That's
>>> required by the standard, so if you do, then you are Doing It Wrong.
>>>
>>> I assume it is pretty easy to turn the warning off.  I'd do it, but I
>>> don't have the Windows build-fu necessary.  Also, do we think it would
>>> require another bug?
>>>
>>
>> Unless someone else can already tell me how I will try to find the
>> cycles to either disable the warning in that file (if that works) else
>> disable it in the build - which will need a new CR I think.
>>
>> David
>>
>>  I'd hate to have to change my (or any) code for this.
>>>
>>> Jeremy
>>>
>>> On Mon, Mar 23, 2015 at 8:48 AM, Kim Barrett <kim.barrett at oracle.com
>>> <mailto:kim.barrett at oracle.com>> wrote:
>>>
>>>     On Mar 23, 2015, at 3:45 AM, David Holmes <david.holmes at oracle.com
>>>     <mailto:david.holmes at oracle.com>> wrote:
>>>     >
>>>     > On 23/03/2015 4:12 PM, David Holmes wrote:
>>>     >> On 21/03/2015 3:32 AM, Jeremy Manson wrote:
>>>     >>> Argh.  Yes.  Martin told me not to get involved with Windows,
>>> but would
>>>     >>> I listen?  Of course not...
>>>     >>>
>>>     >>>http://cr.openjdk.java.net/~jmanson/8074895/webrev.04/
>>>     >>
>>>     >> Looks okay to me - running a test job now.
>>>     >
>>>     > <sigh> This just isn't meant to be :( It seems that:
>>>     >
>>>     > GrowableArray<JavaVMOption> options(2, true);
>>>     >
>>>     > in arguments.cpp is giving the windows compiler some grief:
>>>     >
>>>     >
>>> C:\jprt\T\P1\071814.daholme\s\hotspot\src\share\vm\
>>> utilities/growableArray.hpp(171)
>>> : error C2220: warning treated as error - no 'object' file generated
>>>     >
>>> C:\jprt\T\P1\071814.daholme\s\hotspot\src\share\vm\
>>> utilities/growableArray.hpp(168)
>>> : while compiling class template member function
>>> 'GrowableArray<E>::GrowableArray(int,bool,MEMFLAGS)'
>>>     >        with
>>>     >        [
>>>     >            E=JavaVMOption
>>>     >        ]
>>>     >
>>> C:\jprt\T\P1\071814.daholme\s\hotspot\src\share\vm\runtime\
>>> arguments.cpp(3516)
>>> : see reference to class template instantiation 'GrowableArray<E>'
>>> being compiled
>>>     >        with
>>>     >        [
>>>     >            E=JavaVMOption
>>>     >        ]
>>>     >
>>> C:\jprt\T\P1\071814.daholme\s\hotspot\src\share\vm\
>>> utilities/growableArray.hpp(171)
>>> : warning C4345: behavior change: an object of POD type constructed
>>> with an initializer of the form () will be default-initialized
>>>     >
>>> C:\jprt\T\P1\071814.daholme\s\hotspot\src\share\vm\
>>> utilities/growableArray.hpp(388)
>>> : warning C4345: behavior change: an object of POD type constructed
>>> with an initializer of the form () will be default-initialized
>>>     >
>>> C:\jprt\T\P1\071814.daholme\s\hotspot\src\share\vm\
>>> utilities/growableArray.hpp(379)
>>> : while compiling class template member function 'void
>>> GrowableArray<E>::grow(int)'
>>>     >        with
>>>     >        [
>>>     >            E=JavaVMOption
>>>     >        ]
>>>     >
>>>     > I'm guessing it doesn't like the enum as the generic arg, but
>>> don't know why given that it accepts plain int elsewhere. ???
>>>
>>>     Just suppressing this warning (unconditionally everywhere) would
>>>     probably make sense.
>>>
>>>     Microsoft describes it as an obsolete warning:
>>>
>>>     https://msdn.microsoft.com/en-us/library/wewb47ee.aspx
>>>
>>>     "This warning is obsolete. It is only generated in Visual Studio
>>>     2005 through Visual Studio 2012. It reports a behavior change from
>>>     the Visual C++ compiler that shipped in Visual Studio .NET when
>>>     initializing a POD (plain old data) object with (); the compiler
>>>     default-initializes the object.”
>>>
>>>     It’s too bad the JDK9 supported build platform for Windows is still
>>>     lagging.
>>>
>>>
>>>